JPH11281266A - Vaporization equipment for liquefied natural gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable preventing of excessive spray of water in a vaporizer inexpensively without employing a large flow control valve with a higher flow rate controlling performance as branch tube. SOLUTION: In this vaporization equipment, a liquefied natural gas 6 is vaporized by an open-rack type vaporizer 5 using seawater 3 as heat source. In this case, an adjusting valve 19 is provided in a drain system 9 for draining residual seawater 3 during the cessation of the operation of the vaporizer 5 and a controller 21 is provided to output a command signal 18 to the adjusting valve 19 so that an excess of flow rate of the seawater 3 over a rated flow rate of the evaporator 5 can be drained from the drain system 9 based on a flow rate signal 20 from the existing flowmeter 10 provided on a branch tube 4 for the operational control of the equipment as a whole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquefied natural gas vaporizer using seawater as a heat source.

[0002]

2. Description of the Related Art FIG. 2 shows an example of a conventional liquefied natural gas vaporization facility. In the illustrated vaporization facility, a plurality of seawater pumps 1 provided at a shore or the like are used to guide the gas through a mother pipe 2. The seawater 3 is distributed to a plurality of open rack-type vaporizers 5 connected to the mother pipe 2 via branch pipes 4, and each of the vaporizers 5 performs heat exchange using the seawater 3 as a heat source. As a result, the liquefied natural gas 6 guided from a low-temperature tank (not shown) is vaporized into natural gas 6 ', and the natural gas 6' is delivered to a demand destination such as a thermal power plant.

[0003] Each of the branch pipes 4 is provided with a main valve 7 having a fixed opening individually set so that the seawater 3 can be appropriately distributed according to the capacity of each vaporizer 5. In the middle of the branch pipe 4 downstream of the carburetor 5, the carburetor 5 has a main valve 7 for maintenance and inspection.
A drainage system 9 having an on-off valve 8 is provided so that the residual seawater 3 can be discharged when the operation is shut down and the operation is stopped. A flow meter 10 for measuring a flow rate is provided.

The details of the vaporizer 5 are as shown in FIG. 3, in which the liquefied natural gas 6 introduced from the low-temperature tank into the lower header 11 is heated and vaporized while ascending the heat transfer tube section 12 and vaporized. Natural gas 6 ′ is collected in the upper header 13 and discharged to the demand side, while the seawater 3 guided by the branch pipe 4 is disposed on both sides of the upper header 13 via the seawater pipe 14. The seawater 3 which is supplied to the trough 15 and overflows from the trough 15 flows down while forming a water film on each of the heat transfer tube portions 12 and the fin portions 16 provided between the heat transfer tube portions 12, and receives a water tank. 17 to be discharged.

[0005]

However, in such a conventional liquefied natural gas 6 vaporizer, when any one of the carburetors 5 is shut down for maintenance or the like, the seawater is taken into account. Reduce the number of pumps 1
Although the pump power is lowered or the supply flow rate of seawater 3 to the mother pipe 2 is adjusted, in such a transitional stage where the operating conditions are switched, the operating vaporizer 5 Overflow occurs when the flow rate of the distributed seawater 3 exceeds the rated flow rate. Splashes generated at this time form local voids in the water film, and normal heat exchange takes place in the voids. The temperature distribution changes locally by not being
There is a possibility that thermal stress may act on the heat transfer tube portion 12, the fin portion 16, and the like.

[0006] For this reason, in the vaporization equipment newly installed in recent years, measures are taken to prevent excessive water spraying by adopting a flow control valve instead of the main valve 7 of each branch pipe 4. When the main valve 7 in the existing vaporization equipment as shown in the illustrated example is to be changed to a flow control valve, a normal branch pipe 4 is used.
Since the diameter of the pipe becomes about 1m or more, a large-scale flow control valve is required, and the flow rate can be controlled with high accuracy for a relatively narrow flow control range which is only about 10% of the total flow rate. Since it is technically difficult to perform the process, a flow control valve having a high flow control performance is required, and there is a problem that remodeling of the branch pipe 4 using the flow control valve requires a large cost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and is capable of inexpensively preventing overspray of a vaporizer without employing a large-scale flow control valve having a high flow control performance in a branch pipe. It is intended to provide a liquefied natural gas vaporization facility.

[0008]

According to the present invention, a plurality of open rack type vaporizers are connected via branch pipes to a mother pipe for guiding seawater supplied by a seawater pump, and the capacity of each vaporizer is controlled. A drain valve for discharging the residual seawater at the time when the operation of the evaporator is stopped in the middle of the branch pipe downstream of the main valve, the main pipe having a fixed opening degree so as to appropriately distribute the seawater according to the branch pipe. In a liquefied natural gas vaporization facility with a channel, a control valve is provided at a required position of the drainage system, and a flow meter is provided in the branch pipe,
A control device for outputting a command signal to the control valve so that an excess flow of seawater exceeding a rated flow of the vaporizer can be extracted from the drainage line based on a flow signal from the flowmeter. It is.

Thus, when any one of the carburetors is shut down for maintenance and inspection, the flow rate of seawater distributed to the carburetor in operation increases from the rated flow rate. In addition, it is possible to always extract the surplus flow rate from the drainage line and supply the rated flow rate of seawater to the vaporizer.

Here, the drainage system is only a small-scale auxiliary facility capable of discharging residual seawater when the main valve is closed and the operation of the vaporizer is stopped, and the diameter of the drainage system is the same as that of the branch pipe. Since it is extremely small in comparison, the control valve provided in such a drainage system can be of a small scale, and can be opened at an appropriate degree of opening from a fully closed flow rate of "zero" to achieve high accuracy. It is technically easy to perform high flow adjustment,
There is no need for a control valve with exceptionally high flow control performance.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an embodiment of the present invention, and the portions denoted by the same reference numerals as those in FIG. 2 represent the same components.

The basic structure of the liquefied natural gas vaporization equipment in this embodiment is substantially the same as that of the above-described vaporization equipment shown in FIG. 2, but the on-off valve 8 provided in the conventional drainage system 9 is used.
Instead of (see FIG. 2), a control valve 19 capable of arbitrarily adjusting the opening based on the command signal 18 is provided in the drainage line 9 and provided in the branch pipe 4 for operation and management of the entire equipment. A control device that outputs a command signal 18 to the control valve 19 so that an excess flow rate of the seawater 3 exceeding the rated flow rate of the vaporizer 5 can be extracted from the drainage system 9 based on a flow rate signal 20 from the existing flow meter 10. 21 is characterized.

That is, in the control device 21, the flow rate of the seawater 3 in the branch pipe 4 based on the flow rate signal 20 input from the flow meter 10, the rated flow rate of the vaporizer 5 input as a preset value, and The surplus flow rate of the seawater 3 is calculated from the comparison, and the surplus flow rate is converted into an opening of the control valve 19 of the drainage passage 9 and output as the command signal 18.

If necessary, a signal indicating the operation status of the seawater pump 1 and the vaporizer 5 is derived from a control system for operation and management of the entire equipment, or an existing pressure gauge provided in the main pipe 2 (see FIG. (Not shown), a signal indicating the feed pressure of the seawater 3 in the mother pipe 2 is derived and input to the control device 21. Based on these signals, the feed pressure of the seawater 3 flowing through the branch pipe 4 is adjusted from the pressure balance. It is also possible to calculate and compensate the fluctuation of the supply pressure to control the opening degree of the control valve 19.

Thus, when any one of the carburetors 5 is shut down for maintenance or inspection, the flow rate of the seawater 3 distributed to the carburetor 5 during operation becomes higher than the rated flow rate. Even if it increases, it becomes possible to always extract the surplus flow rate from the drainage line 9 and supply the carburetor 5 with the rated flow rate of seawater 3.

Here, the drainage system 9 is only a small-scale auxiliary facility capable of discharging the residual seawater 3 when the main valve 7 is closed and the carburetor 5 is shut down, and its diameter is small. Is very small as compared with the branch pipe 4, the control valve 19 provided in such a drainage line 9 also needs to be small in size, and moreover, it can be appropriately changed from the fully closed flow "zero" state. Since it is technically easy to perform high-precision flow control by opening the opening, it is not necessary to use a control valve having a particularly high flow control performance, and the existing on-off valve 8 (see FIG. 2) can be used. The remodeling work for laying the control valve 19 can be easily performed.

Therefore, according to the above embodiment, even if a large-scale flow control valve having a high flow control performance is not used for the branch pipe 4, the control valve 1 having a small-scale flow control performance is not particularly high.
Only by providing the drain 9 in the drainage passage 9 and controlling the opening degree, it is possible to prevent inexpensive overspray of the vaporizer 5 and to reliably maintain the soundness of the vaporizer 5.

The liquefied natural gas vaporizer of the present invention comprises:
The present invention is not limited to the above-described embodiment, but may be applied to newly-installed facilities, other than modifying existing facilities, and may be variously modified without departing from the gist of the present invention. Obviously you can get it.

[0020]

According to the above-described liquefied natural gas vaporization equipment of the present invention, even if a large-scale flow control valve having a high flow control performance is not used for the branch pipe, the small-scale flow control performance is extremely high. By merely providing a control valve in the drainage system and controlling the opening, it is possible to prevent inexpensive overspraying of the carburetor and to achieve an excellent effect that the soundness of the carburetor can be reliably maintained. .

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an example of an embodiment of the present invention.

FIG. 2 is a flowchart showing a conventional example.

FIG. 3 is a perspective view showing details of the open rack type vaporizer of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Seawater pump 2 Main pipe 3 Seawater 4 Branch pipe 5 Vaporizer 6 Liquefied natural gas 7 Main valve 9 Drainage system 10 Flow meter 18 Command signal 19 Control valve 20 Flow signal 21 Control device

Claims (1)

[Claims] 1. A plurality of open rack type vaporizers are connected to a mother pipe for guiding seawater supplied by a seawater pump via a branch pipe, and the seawater is appropriately distributed according to the capacity of each vaporizer. Each of the branch pipes is provided with a main valve having a fixed opening so as to obtain a liquefied natural gas which is provided with a drainage passage for discharging residual seawater when the operation of the vaporizer is stopped in the middle of the branch pipe downstream of the main valves. In the vaporization equipment, a control valve is provided at a required position of the drainage system, a flowmeter is provided in the branch pipe, and an excess flow of seawater exceeding the rated flow of the vaporizer is supplied to the drainage system based on a flow signal from the flowmeter. A liquefied natural gas vaporization facility, comprising: a control device that outputs a command signal to the control valve so that the natural gas can be extracted from a road.